PSM pressure vessels built under earlier ASME editions

March 5, 1998

Mr.Wilfred B. Barry, P.E., P.L.S., President
SJB Group, Incorporated
[Recipient address omitted]
Dear Mr. Barry:

Your letter to OSHA's Directorate of Safety and Health Standards related to questions about OSHA's Process Safety Management of Highly Hazardous Chemicals (PSM), 29 CFR 1910.119, was forward to my office. Specifically, your questions are related to the process safety information (PSI) element, 29 CFR 1910.119(d). We apologize for the delay in our response.

The following are your specific questions and OSHA's related responses:

Question 1

Is a previous edition of a current code or standard (i.e. 1972 edition of the Section VIII of the ASME Code) considered to be "a code or standard no longer in general use"?

Reply 1

Yes. This question is generated from OSHA's standard 29 CFR 1910.119(d)(3)(iii). The intent of this requirement is for the employer to determine and document that PSM covered equipment which was designed and constructed to codes, standards or practices which are no longer in general use can continue to operate in a safe manner. After the employer makes the determination required by the standard, it will be the basis for the decision to take the equipment out-of-service or to continue operations. If the equipment is to be kept in-service, the determination will be the baseline from which all future operation, inspection, testing and maintenance is conducted. In making the determination the standard requires the employer to evaluate the design, maintenance, inspection, testing and operation of the PSM covered equipment.

When making the determination required by the standard, OSHA intends that the employer document that PSM covered equipment is consistent with the latest editions of codes and standards. If an employer determines that covered equipment is not in conformance with the latest editions of codes, standards or practices, the employer must document which codes and standards were used and that the design, construction, maintenance, inspection, testing and operation are still suitable for the intended use.

Question 2

Given a pressure vessel designed, constructed, inspected and Code-stamped in accordance with a previous edition of the ASME Code, and for which a manufacturers U-1 form exists, is it necessary to recalculate the vessel's design characteristics (wall thickness, nozzle reinforcement, etc.)?

Reply 2

If the original design and construction is in accordance with the latest edition of design and construction codes and standards for equipment covered by the PSM standard, then OSHA's standard 1910.119(d)(3)(iii) does not require the employer to recalculate design characteristics of PSM covered equipment. However, if there are differences between the original and the latest edition of design and construction codes and standards, then OSHA requires the employer to document those differences. The employer must also show how those differences are consistent with the latest editions of design and construction codes and standards to assure that the equipment can continue to function in a safe manner.

A pressure vessel designed and constructed using any edition of the ASME Code and which posssses a manufacturers' U-1 certification, may have had a change in-service at sometime during its operating history. To assure safe operation the employer when making its determination as required by this standard must also determine and document that the in-service operation, inspection, testing and maintenance of PSM covered equipment considers the change in-service and its impact is consistent with the latest codes, standards and practices so as to assure safe operation.

Question 3

When performing recalculation as a means of establishing suitability for intended service, and given a pressure vessel for which no documentation of material of construction, welding procedures or radiographic testing exists, is it acceptable to assume the lowest value for these variables (i.e. lowest weld joint efficiency factor, lowest allowable stress value for the class of materials involved, etc.) and to incorporate these values into the recalculation?

Reply 3

When an employer conducts an engineering analysis, including recalculation, when no documentation exists for the material of construction, welding procedures or radiographic testing , it is appropriate to assume the lowest value for the listed variables in the engineering analysis as a means of determining that the in-service condition of covered equipment is appropriate for its intended use. The engineering analysis must be conducted in conformance with the latest editions of codes and standards.

If you have any questions related to this letter, please contact Mike Marshall at 202-219-8118 ext. 12.

Sincerely,

John B. Miles, Jr., Director
Directorate of Compliance Programs